JP2015533983A - Time-varying spark current to improve spark plug performance and durability - Google Patents

Abstract

In certain embodiments, a time-varying spark current ignition system may be applied to improve spark plug ignition performance and durability as compared to conventional spark ignition systems. Two performance parameters of interest are spark plug life (durability) and spark plug ignitability. In certain embodiments, the spark plug life is achieved by applying as low a spark current amplitude as possible without causing the flame core to extinguish while the flame kernel is moving through the electrode gap and / or spark / flame. This can be extended by applying a sufficiently long period of spark current to allow the nucleus to pass through the spark plug gap. In certain embodiments, the ignitability is achieved by applying a sufficiently high spark current amplitude to hold the flame kernel once outside the spark plug gap and / or once the flame kernel outside the spark plug gap. This can be improved by applying a spark current for a longer period of time. [Selection figure] None

Description

  This application is the name of the invention entitled “Time-varying Spark Current Magnitude to Improve Spark Plug Performance and Durability” filed on September 17, 2012. Claimed priority of US Patent Application No. 61 / 702,036, and (1) “Two-stage precombustion chamber for large diameter gas engines, filed on September 6, 2013. US Patent Application No. 14 / 020,770 entitled "for large bore gas engines" and "Two-stage precombustion for large bore gas engines" filed on September 6, 2013 International patent application PCT / US13 / 58635 entitled “chamber for large bore gas engines” (both applications are “two-stage pre-combustion chambers for large-diameter gas engines” filed on September 6, 2012). Two-stage precombustion cham ber for large bore gas engines), which claims the priority of US patent application 61 / 697,628, entitled "ber for large bore gas engines)" and (2) "gas engine applications" filed on September 1, 2012 Method and apparatus for achieving high power flame jets while reducing quenching and autoignition in prechamber spark plugs for gas engines ” US patent application Ser. No. 13 / 602,148, filed on Sep. 1, 2012, entitled “High power flame jet with reduced extinction and self-ignition in pre-combustion chamber spark plugs for gas engines” Method and apparatus for achieving high power flame jets while reducing quenching and autoignition in prechamber spark plugs for gas engines " International patent application PCT / US2012 / 53568 (both applications were filed on September 3, 2011, “High-power flame jets were reduced while reducing extinction and self-ignition in pre-combustion chamber spark plugs for gas engines. US Patent Application No. 61 / 573,290 entitled “Method and apparatus for achieving high power flame jets while reducing quenching and autoignition in prechamber spark plugs for gas engines”. (3) U.S. Patent Application No. 13 / 997,680 entitled "Prechamber Ignition System" filed on June 25, 2013 (U.S. Patent Application No. No. 13 / 997,680 is an international patent issued under the name of the invention of “Prechamber Ignition System” filed on December 30, 2011. PCT / US2011 / 002012 claims priority and its international patent application was filed on December 31, 2010, “High efficiency ricochet effect passive chamber spark plug”. Claiming priority of US patent application No. 61 / 460,337 in the name of the invention) and (4) “Active Scavenge Prechamber” filed on March 12, 2013. No. 61 / 778,266 in the name of the present invention. The entirety of each of the aforementioned patent applications is hereby incorporated by reference in its entirety.

  The present disclosure relates generally to systems and methods for changing spark current over time to improve spark plug performance and durability.

  There are a variety of different electrode gap types utilized by industrial spark plug manufacturers. Some claim better ignitability (less flame extinction) and others claim improved durability (plug life). Many high energy systems can meet the ignition requirements, but design tradeoffs to achieve this performance can have a negative impact on spark plug life.

  There is a need in the art to address the aforementioned deficiencies.

FIGS. 1 a-1 c illustrate an exemplary MSP (multi-torch spark plug) type spark gap in a spark plug with a small surface area to volume ratio, according to an embodiment. 2a-2c show an exemplary double bar spark plug with a small surface area to volume ratio, according to an embodiment. 3a-3c illustrate an exemplary annular spark plug with a large surface area to volume ratio, according to an embodiment. 4a-4c show an exemplary annular spark plug with a large surface area to volume ratio, according to an embodiment. 5a-5c show an exemplary three-prong spark plug with a large surface area to volume ratio, according to an embodiment. FIG. 6 illustrates a flame kernel growth sequence for an exemplary spark plug gap design, according to an embodiment. FIG. 7a shows an exemplary three-prong spark plug, according to an embodiment. FIG. 7b shows a flame kernel growth sequence for the spark plug type of FIG. 7a with two different gap sizes 0.010 "and 0.016" according to an embodiment. FIG. 8 shows a flame kernel growth sequence for the spark plug type of FIG. 7a with two different gap sizes 0.010 "and 0.016" according to an embodiment. FIG. 9 illustrates a typical CPU 95 (low energy) spark discharge waveform according to an embodiment. FIG. 10 illustrates a flow field analysis of a three prong spark plug according to an embodiment. FIG. 11 shows the λ distribution of a three prong spark plug, according to an embodiment. FIG. 12 illustrates a DEIS high energy spark optimization waveform according to an embodiment. FIG. 13 illustrates a time varying current according to an embodiment. Figures 14a-14b show a conventional ignition system with a significantly reduced spark current. FIG. 15 illustrates a time-varying spark current ignition system and resulting spark movement, according to an embodiment. FIG. 16 illustrates flame kernel growth using a time-varying spark current according to an embodiment. FIG. 17 illustrates flame kernel growth using a conventional spark discharge, according to an embodiment. FIG. 18 shows a chart comparing combustion pressure curves using time-varying spark current and conventional spark current, according to one embodiment using conventional spark current. FIG. 19 shows spark breakdown voltage versus spark plug durability comparing time-varying spark current and conventional spark current. 20a-20c show examples of spark gaps with a large surface area to volume ratio, according to an embodiment.

In one embodiment, a method of changing a spark current, comprising providing a spark plug including a main electrode and one or more ground electrodes offset from the main electrode to form one or more electrode gaps; Disposing a spark plug to dispose a main electrode and one or more grounded electrodes in a combustion chamber of an internal combustion engine, introducing a flow of fuel / air mixture through one or more electrode gaps; Disclosed is a method including introducing a spark current across at least one of the one or more electrode gaps to ignite and increasing the spark current to grow a spark channel. Increasing the spark current may include gradually increasing the spark current. Increasing the spark current may include increasing the spark current at a rate that is approximately proportional to the rate of increase of the spark movement. Increasing the spark current may include increasing the spark current based at least in part on the flow characteristics of the fuel-air mixture. The flow characteristic may include a variation in flow momentum. Increasing the spark current may include increasing the spark current at a rate approximately proportional to the increase in flow momentum. Increasing the spark current may include increasing the spark current based at least in part on at least one geometric characteristic of the one or more electrode gaps. Increasing the spark current may include increasing the spark current over a distance traveled by the spark channel at a ratio approximately proportional to the variation of the electrode gap surface area to volume ratio. The main electrode and the one or more ground electrodes may define an electrode surface area to electrode gap volume ratio greater than about 3.0 mm ⁻¹ . The one or more electrode gaps may include a substantially uniform flow of the fuel air mixture. The substantially uniform flow may have a minimum speed of about 3 m / s. The method may further include determining the electrode surface temperature and adjusting the amount of spark current in response to the electrode surface temperature. The method may further include determining an increase in pressure in the combustion chamber and aborting the application of the spark current if the increase in pressure exceeds a predetermined threshold. The method may further include determining flame nucleation in the electrode gap and aborting the application of the spark current if the flame nucleation exceeds a predetermined threshold. Increasing the spark current may include increasing the spark current from an onset of less than about 150 mA to greater than about 150 mA, producing a flow rate of less than about 3 m / s at one or more electrode gaps. The above electrode gap includes a surface area to volume ratio greater than about 3 mm ⁻¹ .

In one embodiment, a pre-combustion chamber spark plug, the outer surface and the inner surface surrounding the pre-combustion chamber volume, and one or more between the outer surface and the inner surface for introducing a fuel air mixture into the pre-combustion chamber volume A pre-combustion chamber, a main electrode disposed within the pre-combustion chamber volume, and one or more electrode gaps configured to introduce a time-varying spark current across the one or more electrode gaps. A precombustion chamber spark plug is disclosed that includes one or more ground electrodes disposed within the volume and offset from the main electrode. The time-varying spark current may include a gradually increasing spark current. The time-varying spark current may include a spark current that increases at a rate approximately proportional to the rate of increase of spark movement. The time-varying spark current may include a spark current that increases based at least in part on the flow characteristics of the air or fuel-air mixture. The flow characteristic may include a variation in flow momentum. The time-varying spark current may include a spark current that increases at a rate approximately proportional to the increase in flow momentum. The time-varying spark current may include a spark current that increases based at least in part on the geometric characteristics of the electrode spark gap. The time-varying spark current may increase over a distance traveled by the spark channel at a rate approximately proportional to the variation in electrode gap surface area to volume fraction. The main electrode and the one or more ground electrodes may define an electrode gap surface area to volume ratio greater than about 3.0 mm ⁻¹ . The precombustion chamber spark plug may further include a substantially uniform fuel air mixture flow through one or more electrode spark gaps. The substantially uniform flow may have a minimum speed of about 3 m / s. The time-varying spark current may vary with time based at least in part on the magnitude of the velocity of the fuel-air mixture flow through one or more electrode gaps, and the electrode gap surface area to volume ratio. The time-varying spark current may begin at less than about 150 mA and terminate with a flow rate greater than about 150 mA, less than about 3 m / s at one or more electrode gaps, and an electrode gap surface area to volume ratio greater than 3 mm ^−1. May be. The time-varying spark current amount may be adjusted according to the electrode surface temperature. The spark current may be configured to be aborted when the pressure increase exceeds a predetermined threshold. The spark current may be configured to be aborted when flame kernel growth exceeds a predetermined threshold.

  For the purposes of this application, “gradually” means that the rate of increase in current is proportional to the rate of increase in spark movement due to flow momentum, where flow momentum is the flow mass density acting on the spark × flow velocity. May be defined as For example, but not limited to, the increase in the amount of current may be zero when the spark movement rate is constant. For example, but not limited to, when the spark transfer rate is doubled, the amount of current may also be doubled.

  In certain embodiments, the flow characteristics may include variations in flow momentum, which may be defined as flow mass density × flow velocity. In certain embodiments, the increase in the amount of spark current may be proportional to the increase in flow momentum. For example, but not limited to, if the flow momentum is constant, the amount of current may also be constant. For example, but not limited to, if the flow momentum is doubled, the amount of current may also be doubled.

  In certain embodiments, the geometric properties may include, but are not limited to, variations in electrode gap surface area to volume fraction over the distance traveled by the spark. In certain embodiments, the increase in spark current may be proportional to the variation in electrode gap surface area to volume ratio over the distance traveled by the spark. For example, without limitation, the increase in the amount of current may be zero if the surface area to volume ratio is constant throughout the distance traveled by the spark. For example, but not by way of limitation, if the surface area to volume ratio doubles over the distance traveled by the spark, the amount of current may also double.

  In certain embodiments, spark plug performance can be improved by applying a time-varying spark current to improve performance and durability as compared to conventional spark plug designs. Two performance parameters of interest are spark plug life and spark plug ignitability. In some embodiments, the spark plug life can be extended by applying as low a spark current amplitude as possible without causing the flame kernel to extinguish while the flame kernel is moving through the spark plug gap. In certain embodiments, the spark plug life can be extended by applying a sufficiently long period of spark current to allow the spark / flame core to pass through the spark plug gap. In certain embodiments, ignitability can be improved by applying a sufficiently high spark current amplitude to hold the flame kernel once outside the spark plug gap. In certain embodiments, ignitability can be improved by applying a spark current for a time period long enough to hold the flame kernel once outside the spark plug gap.

In certain embodiments, regardless of electrode shape, an important factor affecting ignitability is the surface area to volume ratio (S / V), which is between the electrode surface area and the gap volume limited between the surfaces. Defined as the ratio of In certain embodiments, for the same flame kernel size, the heat loss to the surface of the electrode increases in proportion to the size of the surface. The following are some examples of electrode gaps, their S / V, and how they ultimately affect flame kernel propagation. In some embodiments, the S / V may be considered small if it is 4 mm ⁻¹ or less.

In one embodiment, the images of FIGS. 1 a-1 c show the S / V for an MSP (Multi Torch Spark Plug) 100 type spark gap in a spark plug. The spark plug geometry is shown in this case because the shell acts as the ground electrode 120. As can be seen in the image, the center electrode 110 is very small and sparks into the shell. This geometric shape can be classified as having a small S / V (about 4 mm ⁻¹ ). In certain embodiments, another exemplary spark plug having a low S / V electrode geometry comprises about 1.2 mm ⁻¹ S / V, as shown in FIGS. 2a-2c. , A double bar 200 type spark gap including a main electrode 210 and a double bar shaped ground electrode 220.

  In some embodiments, examples of electrode gaps with large electrodes S / V include, but are not limited to, the annular gap 300 of FIGS. 3a-3c, and the particular J gap type spark of FIGS. 4a-4c. It may include a plug 400 and the three-prong gap 500 of FIGS. 5a-5c. 3a-3c represent the main electrode 310 and the annular ground electrode 320. FIG. FIGS. 4 a-4 c show the main electrode 410 and the J-shaped ground electrode 420. 5a to 5c show the main electrode 510 and the prong-type ground electrode 520. FIG. This J-gap, patented by Denso, also has a cross groove on the cathode (high voltage or main electrode) that helps in reducing the S / V of the gap.

  In one embodiment, as shown in FIG. 6, a double bar electrode 200 and J gap 400 combustion simulation results in confirming that the S / V ratio of each design dominates flame kernel growth. . FIG. 6 provides a comparison of flame nucleation sequences for two different S / V ratio plug designs. The spark timing and spark energy for both plugs are the same. As expected, flame kernels with designs with smaller S / V ratios (in this case, double bars 200) grow more rapidly. This is because it has less heat loss and more of its energy can go towards flame propagation.

In some embodiments, to further demonstrate that the results obtained with the sequence shown in FIG. 6 were not affected by factors other than the flow field or S / V, the same plug-type gap size was used. The survey was carried out by changing This actually changes the S / V of the plug. The plug selected for this simulation was a 3-prong 500 model. Shown in FIGS. 7a-7b and 8 is a sequence of flame kernel 530 growth using the same spark energy for two different gap sizes 0.010 "and 0.016". Large S / V (7.8 mm ⁻¹ , small gap) has higher heat loss to the electrode, resulting in slower flame growth and smaller flame kernel 530 size exiting the gap. On the other hand, a larger gap size (S / V = 4.9 mm ⁻¹ ) reduces heat loss, improves flame kernel 530 growth rate, and allows a larger flame kernel 530 size to exit the gap. did.

  In certain embodiments, general criteria for optimization may include adjusting the spark waveform, λ distribution, and electrode gap design for flow field velocity. In certain embodiments, the spark waveform may be selected to meet certain ignitability and electrode corrosion criteria, which may be referred to as an ignitability (performance) / plug life tradeoff.

  In certain embodiments, with respect to the ignitability criteria, the initial flame kernel may move sufficiently quickly through the gap to minimize heat loss and thus minimize extinction. To achieve this, there may be a suitable flow field as well as a suitable spark size to provide the necessary aerodynamic resistance characteristics. In certain embodiments, the spark energy delivery rate may offset the heat loss from the flame kernel to the electrode surface.

  Although many high energy systems can meet the above ignitability requirements, design tradeoffs to achieve this performance can negatively impact spark plug life. In certain embodiments, for spark optimization, the energy rate delivered in the spark may be high enough to produce a consistent flame kernel. In certain embodiments, any excess energy delivered in the spark can negatively affect plug life without providing any benefit.

  In certain embodiments, an exemplary process for optimizing a spark waveform for a particular application is displayed. In certain embodiments, it is desirable to develop a spark waveform that increases combustion stability with thinner air-fuel ratio operation without compromising electrode wear rates. In some embodiments, the waveform of FIG. 9 may be used, and the waveform may be a standard CPU 95 (low energy) spark discharge. In certain embodiments, higher energy with sufficient travel time (long duration) meets the desired properties. A programmable high energy DEIS may be used to generate the required spark waveform.

  In some embodiments, the flow field of the electrode gap of the spark plug used for the application may be studied to determine the shape of the waveform. In some embodiments, a three-prong gap 500 may be used. CFD simulations may be performed using engine geometry and settings specific to a particular application. The flow fields for three different gaps are shown in FIG. They may be similar to those observed in the simulation results discussed above. The flow varies for each ground electrode in both magnitude and direction.

  In certain embodiments, examination of the λ distribution for each electrode gap may show a relatively similar distribution in all three gaps as shown in FIG. In some embodiments, the flame kernel growth variation may be approximately a function of the electrode gap flow field.

  In certain embodiments, the waveform may be adjusted so that it generates a sufficiently large spark that moves with a flow field having a magnitude of about 1-5 m / s. In certain embodiments, the spark waveform may be long enough to move the distance of the electrode surface. In certain embodiments where the flame kernel may move toward the core nose, the mixture distribution may be sufficiently abundant to prevent quenching. The flame kernel may grow slower than other spark locations, but this may be specific to the selected plug and flow field specific to this application.

  In some embodiments, the waveform shown in FIG. 12 may be used. It can be the optimal waveform for a particular application based on the requirements outlined above. The current amplitude may be high enough (100-300 mA) to produce a large diameter plasma column that moves with the flow. The duration may be long enough (1250 μs) to allow the flame kernel enveloping the spark to exit the electrode gap. In certain embodiments, the energy delivery profile may be such that it maintains flame kernel growth without compromising electrode erosion wear (plug life).

In certain embodiments, the spark discharge can be varied to produce consistent flame nucleation. In certain embodiments, the spark waveform optimization process may follow the following steps.
a. Defining application requirements and constraints.
b. Examining the flow field and λ distribution of the electrode gap.
c. Using a programmable high energy DC ignition system to adjust the spark to meet the flow field and mixture distribution requirements.
d. Designing a spark waveform that optimizes the ignitability / plug life tradeoff.

  In certain embodiments, the spark current may be varied over time as shown in FIG. After the start of spark 1310, the spark current can be increased linearly over a period of about 500-600 μs to a spark current of about 100 mA, and the rate of increase in spark current can be increased at a point of about 100 mA. As indicated at 1320, the flame kernel first travels within the gap, and then when the flame kernel reaches the end of the gap, the spark is external to the gap as indicated at 1330. Extend to. As indicated by the gray bar 1340, once flame kernel growth has begun, the rate of increase of the spark current may be reduced. Those skilled in the art will appreciate that various time-varying spark current profiles are possible without departing from the scope of the present invention.

As shown in FIGS. 14a-14b, conventional ignition systems have a significantly reduced spark current. For example, as shown in FIG. 14a, a conventional ignition system may have a spark current profile that reaches an apex at 100 mA at the start of the spark and then linearly decreases to zero within 200 μs. A spark 1410 may be generated between the main electrode 1420 and the ground electrode 1430, but the spark may not move along the electrode gap due to low current and short discharge duration. FIG. 14b displays another conventional spark current profile with a slightly higher peak current of 150 mA and a spark duration of about 300 μs before the spark current returns to zero and the spark stops. A spark 1410 may be generated at T ₁ between the main electrode 1420 and the ground electrode 1430, but the spark 1410 may be from T ₁ (yellow) to T ₂ (orange due to insufficient current and discharge periods. ) May have limited movement up to.

In certain embodiments, a time-varying spark current ignition system can be used to improve spark plug performance. Time-varying spark current ignition system achieves high power flame jet while reducing extinguishing and self-ignition with conventional spark plugs or filed on September 1, 2012 "pre-combustion chamber spark plugs for gas engines US patent application Ser. No. 13 / 602,148, co-pending the title of “Method and apparatus for achieving high power flame jets while reducing quenching and autoignition in prechamber spark plugs for gas engines” US patent application Ser. No. 13 / 997,680 entitled “Prechamber Ignition System” filed on June 25, 2013, and filed March 12, 2013, “ US patent application Ser. No. 61 / 778,266 entitled “Active Scavenge Prechamber” (All of these applications are incorporated in their entirety. With prechamber spark plug such as described in incorporated) herein by Oite reference, it may be used. As shown in FIG. 15, the time-varying spark current has a significantly increasing spark current that can produce an efficient spark that travels because of the continuous increase in the spark current over time as shown. May be. In some embodiments, a spark 1510 is created between the main electrode 1520 and the ground electrode 1530 and moves from T ₁ (yellow) to T ₂ (orange) and to T3 (red) as shown. May be.

  In one embodiment, as shown in FIG. 16, the use of a time-varying spark current profile results in a conventional spark discharge as shown in FIG. 17 resulting in substantially smaller flame kernel 1710 growth. In comparison, a much stronger flame kernel 1610 growth can be produced.

  In some embodiments, such as that shown in FIG. 18, the use of a time-varying spark current profile can result in a stable and efficient combustion as shown in region 1810 of FIG. The use of a conventional spark current profile can result in unstable and inefficient combustion as shown in region 1820 of FIG.

  In certain embodiments, such as shown in FIG. 19, the use of a time-varying spark current profile represented by the green dotted line 1910 may indicate a lower electrode gap growth rate due to spark (or arc) movement. In contrast, the conventional spark current profile represented by the red dotted line 1920 may have a high electrode gap growth rate because of a static arc (or spark). As a result, the use of a time-varying spark current profile can result in significantly improved spark plug durability, as shown in FIG. One skilled in the art will appreciate that the term spark or arc is interchangeable in the context of spark or arc movement.

  Those skilled in the art will appreciate that the systems and methods described above can be used with a variety of spark gap configurations, including but not limited to the large surface area to volume fraction configurations shown in FIGS. 20a-20c. Like.

  While the above description includes many details, and certain exemplary embodiments have been described and illustrated in the accompanying drawings, such embodiments are merely illustrative of the broad invention and It should be understood that this is not a limitation and that the present invention is not limited to the specific structures and arrangements shown and described. This is because, as noted above, various other modifications will occur to those skilled in the art. The present invention includes any combination or subcombination of elements from the different types and / or embodiments disclosed herein.

  Although the invention has been described with reference to specific embodiments thereof, various modifications can be made and equivalents depart from the spirit and scope of the invention as defined by the appended claims. It should be understood by those skilled in the art that they can be substituted without. In addition, many modifications may be made to adapt a particular situation, material, composition of matter, method, operation to the objective, spirit and scope of the present invention. All such modifications are intended to be within the scope of the claims appended hereto. In particular, although the methods disclosed herein have been described in connection with particular operations performed in a particular order, these operations are equivalent methods without departing from the teachings of the present invention. It will be understood that they may be combined, subdivided, or rearranged to form. Accordingly, unless otherwise indicated herein, the order of operations and grouping is not a limitation of the present invention.

Claims (31)

A method of changing the spark current,
Providing a spark plug including a main electrode and one or more ground electrodes offset from the main electrode to form one or more electrode gaps;
Disposing the spark plug to dispose the main electrode and one or more ground electrodes in a combustion chamber of an internal combustion engine;
Introducing a flow of fuel-air mixture through the one or more electrode gaps;
Introducing a spark current across at least one of the one or more electrode gaps to ignite the fuel-air mixture;
Increasing the spark current to grow a spark channel.   The method of claim 1, wherein increasing the spark current comprises gradually increasing the spark current.   The method of claim 2, wherein increasing the spark current comprises increasing the spark current at a rate that is approximately proportional to a rate of increase in spark movement.   The method of claim 1, wherein increasing the spark current comprises increasing the spark current based at least in part on a flow characteristic of a fuel-air mixture.   The method of claim 4, wherein the flow characteristic comprises a variation in flow momentum.   The method of claim 1, wherein increasing the spark current comprises increasing the spark current at a rate approximately proportional to an increase in flow momentum.   The method of claim 1, wherein increasing the spark current comprises increasing the spark current based at least in part on at least one geometric characteristic of the one or more electrode gaps.   2. Increasing the spark current comprises increasing the spark current over a distance traveled by the spark channel at a ratio approximately proportional to a variation in electrode gap surface area to volume ratio. Method. The method of claim 1, wherein the main electrode and the one or more ground electrodes define an electrode surface area to electrode gap volume ratio greater than about 3.0 mm ⁻¹ .   The method of claim 1, wherein the one or more electrode gaps comprise a substantially uniform flow of a fuel air mixture.   The method of claim 10, wherein the substantially uniform flow has a minimum velocity of about 3 m / s. Determining an electrode surface temperature;
The method according to claim 1, further comprising adjusting the amount of spark current according to the electrode surface temperature. Determining a pressure increase in the combustion chamber;
The method of claim 1, further comprising: terminating application of the spark current if the pressure increase exceeds a predetermined threshold. Determining flame nucleation in the electrode gap;
2. The method of claim 1, further comprising: terminating the application of the spark current when the flame nucleation exceeds a predetermined threshold. Increasing the spark current includes increasing the spark current from an onset of less than about 150 mA to greater than about 150 mA to produce a flow rate of less than about 3 m / s in the one or more electrode gaps; The method of claim 1, wherein the one or more electrode gaps comprise a surface area to volume ratio greater than about 3 mm ⁻¹ . An outer surface and an inner surface surrounding the precombustion chamber volume;
One or more holes communicating between the outer surface and the inner surface for introducing a fuel-air mixture into the precombustion chamber volume;
A main electrode disposed within the precombustion chamber volume;
1 disposed within the precombustion chamber volume and offset from the main electrode to form the one or more electrode gaps configured to introduce a time-varying spark current across the one or more electrode gaps. A pre-combustion chamber spark plug comprising the above ground electrode.   The pre-combustion chamber spark plug of claim 16, wherein the time-varying spark current comprises a progressively increasing spark current.   The pre-combustion chamber spark plug of claim 16, wherein the time-varying spark current comprises a spark current that increases at a rate approximately proportional to a rate of increase in spark travel.   The pre-combustion chamber spark plug of claim 16, wherein the time-varying spark current comprises a spark current that increases based at least in part on the flow characteristics of the air or fuel-air mixture.   The pre-combustion chamber spark plug of claim 19, wherein the flow characteristic includes a variation in flow momentum.   The pre-combustion chamber spark plug of claim 16, wherein the time-varying spark current comprises a spark current that increases at a rate approximately proportional to an increase in flow momentum.   The pre-combustion chamber spark plug of claim 16, wherein the time-varying spark current comprises a spark current that increases based at least in part on a geometric characteristic of the electrode spark gap.   The pre-combustion chamber spark plug of claim 16, wherein the time-varying spark current increases over a distance traveled by the spark channel at a rate approximately proportional to a variation in electrode gap surface area to volume fraction. The pre-combustion chamber spark plug of claim 16, wherein the main electrode and the one or more ground electrodes define an electrode gap surface area to volume ratio of greater than about 3.0 mm ⁻¹ .   The precombustion chamber spark plug of claim 16, further comprising a substantially uniform flow of a fuel air mixture through the one or more electrode gaps.   26. A pre-combustion chamber spark plug according to claim 25, wherein the substantially uniform flow has a minimum velocity of about 3 m / s.   17. The time-varying spark current varies with time, based at least in part on the magnitude of the velocity of fuel-air mixture flow through the one or more electrode gaps, and electrode gap surface area to volume ratio. Pre-combustion chamber spark plug as described. The time-varying spark current begins at less than about 150 mA and ends at greater than about 150 mA, the flow rate at the one or more electrode gaps is less than about 3 m / s, and the electrode gap surface area to volume ratio is about 3 mm. The pre-combustion chamber spark plug of claim 16, greater than ⁻¹ .   The pre-combustion chamber spark plug according to claim 16, wherein the magnitude of the time-varying spark current is adjusted according to the electrode surface temperature.   The pre-combustion chamber spark plug of claim 16, wherein the spark current is configured to be terminated when the pressure increase exceeds a predetermined threshold.   The pre-combustion chamber spark plug of claim 16, wherein the spark current is configured to be terminated when the flame kernel growth exceeds a predetermined threshold.

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